It’s extremely important to study a species’ foraging behavior, since how—and how much—an animal eats can help us understand its physiology, energy use, and fitness. But when it comes to animals that find their food underwater, such as penguins, whales, and fish, it’s often difficult for scientists to get accurate measures of foraging success. Now, two Japanese scientists have used penguin-mounted video cameras in tandem with tiny accelerometers to get extremely accurate information about the foraging behavior of penguins and other diving animals. Their research, along with some fantastic video, was published this week in PNAS.

The scientists wanted to test how well head acceleration—a commonly-used proxy for prey capture—reflects actual foraging success in wild penguins. The assumption is that, when a diving animal’s head accelerates quickly in relation to its body, the animal is catching prey. However, there are questions about how accurately head acceleration represents prey capture rate; for instance, animals may occasionally "miss" their prey, and quick head movements may occur during behaviors other than prey capture.

To test this proxy, the researchers attached 9-gram accelerometers to the heads and the backs of 13 wild Adélie penguins, which averaged nearly 4 kg each. By comparing the acceleration of the penguins’ heads to the rest of their bodies, the researchers could determine relative head acceleration during their foraging dives. They added 33-gram video cameras to the penguins’ backs as well; these cameras could confirm whether head acceleration actually reflected successful prey capture.

From the hours of diving footage, one thing was clear: these penguins are incredibly successful foragers. Not one penguin was ever observed “missing” any prey item during the taped dives. Furthermore, the penguins were extremely fast at snatching their prey, catching up to two krill per second and as many as 14 fish in 20 seconds. Take a look at the researchers’ video of penguins capturing krill [11MB mov] and an Antarctic fish called the bald notothen [10MB mov].

The penguins' head accelerations coincided extremely well with prey captures and when taken with the low miss rate this suggests that head acceleration may be a good proxy for foraging success in this species. However, the researchers noticed that head accelerations also occurred when penguins were searching along the sea floor, moving their heads from side to side to look for prey. Therefore, they caution that studying distinct types of foraging—such as diving versus seabed searching—may require the use of different proxies.

Upon studying the penguins’ foraging behavior, another pattern also became clear. Generally, scientists use a normal distribution to describe the foraging success of diving animals; in this type of distribution, the average value (in this example, the average success of an individual’s foraging dives) gives a pretty accurate picture of the phenomena. However, data from this study suggest that a power-law distribution may work better than a normal distribution. This difference is important because in a power-law distribution there is so much variation that the average value isn’t very informative. Instead, the feeding success of penguins (and perhaps other underwater foragers as well) may hinge on a very small number of highly profitable dives.

While video cameras and accelerometers aren’t an efficient or cost-effective way to study foraging behavior over the long term, they are an excellent way to test and validate proxies for prey capture. Having a better idea of how diving animals forage—and having reliable ways to study this phenomenon—will give us insight into the behavior of underwater animals, as well as the structure and health of their ecosystem.

Promoted Comments

I was confused by the picture until I saw the video. We're looking at the back of a penguin's head, accelerometer attached, as it is swimming under an ice sheet, looking up towards the surface (algae hanging down from the ice) about to strike at a fish.

21 Reader Comments

I was confused by the picture until I saw the video. We're looking at the back of a penguin's head, accelerometer attached, as it is swimming under an ice sheet, looking up towards the surface (algae hanging down from the ice) about to strike at a fish.

Nice to hear that research from two Japanese scientists was published in PNAS, but why keep their names a secret and then fail to link to the actual paper? (The link at the end of the article is a dead end.)

I'm interested in taking a deeper look at this research but this writeup doesn't make that possible.

Nice to hear that research from two Japanese scientists was published in PNAS, but why keep their names a secret and then fail to link to the actual paper? (The link at the end of the article is a dead end.)

I'm interested in taking a deeper look at this research but this writeup doesn't make that possible.

Nice to hear that research from two Japanese scientists was published in PNAS, but why keep their names a secret and then fail to link to the actual paper? (The link at the end of the article is a dead end.)

There is a link right next to that which says About DOIs. If you're going to read science coverage on Ars, it's probably best to click that and read through it first.

I was confused by the picture until I saw the video. We're looking at the back of a penguin's head, accelerometer attached, as it is swimming under an ice sheet, looking up towards the surface (algae hanging down from the ice) about to strike at a fish.

I have nothing towards your comment but "Editor's Pick"? Too soon for comment of the post? Or am I misunderstanding the yellow badge?

All I can say is can someone teach all these people to use modern video container formats? lol. You know it is bad when ALL of them are in gstreamer-plugins-bad-obsure-extra-ugly-neversawthisbefore, lol.

On a more serious note, it's been shown a while back that attaching things to animals - even something as simple as a ring around their leg for tracking - has a significant effect on their behaviour. That's not to say that the data in this study is crap, but perhaps that penguin would have caught 20 fish instead of 14 in those 20 seconds. Or maybe it tried harder because it wanted to look awesome.

davegermain wrote:

In the world of youtube why on earth have these been embedded in a page as MOV files, i want to see the video but don't want to install more software to see it.

any one got an official youtube link to he video?

As far as I know, PNAS doesn't allow Youtube videos to be submitted as supplementary data - authors must submit the original video files. However, I found these Youtube videos:

All I can say is can someone teach all these people to use modern video container formats? lol. You know it is bad when ALL of them are in gstreamer-plugins-bad-obsure-extra-ugly-neversawthisbefore, lol.

At least it is mpeg4/AAC, and not mjpeg or rv or some other terrible thing.But yeah, even Apple doesn't use .mov anymore.

All I can say is can someone teach all these people to use modern video container formats? lol. You know it is bad when ALL of them are in gstreamer-plugins-bad-obsure-extra-ugly-neversawthisbefore, lol.

.mov is on the (very) short list of video containers PNAS allows for supplementary material.

Just be glad that the authors didn't choose Animated GIF...also on that short list.

All I can say is can someone teach all these people to use modern video container formats? lol. You know it is bad when ALL of them are in gstreamer-plugins-bad-obsure-extra-ugly-neversawthisbefore, lol.

.mov is on the (very) short list of video containers PNAS allows for supplementary material.

Just be glad that the authors didn't choose Animated GIF...also on that short list.

Good job on differentiating between container and encoding there, guys. Apparently an .avi with rm, mjpeg, or indeo content is fine. But it also says "MPEG files" so the way I see it you are free to use at least h264/AAC/.mp4 format. No open formats, of course... in the other sections, I see Excel as a valid dataset format. Ugh.

All I can say is can someone teach all these people to use modern video container formats? lol. You know it is bad when ALL of them are in gstreamer-plugins-bad-obsure-extra-ugly-neversawthisbefore, lol.

No kidding. I didn't finish the article because I side stepped to codec support in (stupid) chrome and how it refuses to open QuickTime when I had already installed the piece of bloat crap along with iTunes in my computer. Yes I have VLC installed along with MPC but somehow it opens as in "save as". I don;t understand their choice of mov's...

I was confused by the picture until I saw the video. We're looking at the back of a penguin's head, accelerometer attached, as it is swimming under an ice sheet, looking up towards the surface (algae hanging down from the ice) about to strike at a fish.

I have nothing towards your comment but "Editor's Pick"? Too soon for comment of the post? Or am I misunderstanding the yellow badge?

Perhaps it was selected because it could potentially help clarify things for a great number of other readers who also had trouble deciphering the photo.

Kate Shaw Yoshida / Kate is a science writer for Ars Technica. She recently earned a dual Ph.D. in Zoology and Ecology, Evolutionary Biology and Behavior from Michigan State University, studying the social behavior of wild spotted hyenas.